Sporadic late‐onset nemaline myopathy as a rare cause of slowly progressive muscle weakness with young adult onset

Introduction: Sporadic late‐onset nemaline myopathy (SLONM) is a rare intractable acquired myopathy characterized by progressive muscle weakness and atrophy, usually with middle to late adult onset. Autologous peripheral blood stem cell transplantation (auto‐PBSCT) has been reported to be a promising treatment for SLONM. Methods: In this study we performed clinical characterization, muscle histopathological analysis, and muscle power monitoring after auto‐PBSCT in a 27‐year‐old HIV‐negative man with monoclonal gammopathy. Results: He showed improved muscle strength after treatment with high‐dose melphalan and auto‐PBSCT. Conclusions: Considering the recent reports of successful treatment of SLONM, early and correct diagnosis of this condition in association with monoclonal gammopathy is important. SLONM should be added to the list of diseases to consider in the differential diagnosis of progressive muscle weakness with young adult onset. Muscle Nerve 51 :772–774, 2015     

Sporadic late onset nemaline myopathy responsive to IVIg and immunotherapy

Sporadic late onset nemaline myopathy (SLONM) is a progressive myopathy of indeterminate etiology and poor outcome. If associated with a monoclonal gammopathy, SLONM carries a more unfavorable prognosis. Immunotherapy was unsuccessful. We report two HIV‐negative SLONM/monoclonal gammopathy patients who improved following intravenous immunoglobulin (IVIg) treatment alone or in combination with immunosuppressant agents. This favorable response to treatment suggests that a dysimmune mechanism is operative in some SLONM individuals. We suggest that IVIg deserves initial consideration for SLONM therapy. Muscle Nerve, 2010     

Electromyography in congenital nemaline myopathy

To clarify the discrepancies between earlier reports of electromyography (EMG) in congenital nemaline myopathy (CNM), conventional electromyography was done on 13 patients with CNM, and results were compared with those of 18 earlier EMG examinations of the same patients. Fiber density was measured in 10 patients with a computerized method and neuromuscular jitter in 3 with single-fiber EMG. With age, the EMG abnormality progressed, and "neuropathic" EMG features developed in distal muscles. In 9 of 10 patients fiber density was higher than normal. In two of three patients jitter was abnormal. Motor (13 of 13 patients) and sensory (3 of 3 patients) nerve conduction velocities were normal. Our results seem to explain the conflicting reports of EMG in CNM. We conclude that active degeneration and regeneration of muscle fibers takes place in CNM and suggest that the "neuropathic" motor unit potentials seen in our patients may be secondary to myopathic disease activity.     

Co‐existence of nemaline and cytoplasmic bodies in muscle of an infant with nemaline myopathy

A sporadic case of congenital myopathy had severe muscle weakness of neonatal onset. Nemaline and cytoplasmic bodies were detected in muscle biopsies taken at 4 months of age. These findings were consistent with a diagnosis of nemaline myopathy (severe neonatal form). The simultaneous and abundant presence of these two types of sarcoplasmic inclusion has been found in only a few cases. However, these cases suggest that the sarcoplasmic inclusions may be formed, at least partially, by common mechanisms.     

Neonatal nemaline myopathy with abundant intranuclear rods

A term hypotonic female infant was born to a primigravida mother. The infant required mechanical ventilation from birth until death at 5 weeks of age. An elevated serum creatine kinase of 1300 IU l⁻¹ lead to a quadriceps muscle biopsy at 3 days of age. The biopsy showed numerous intranuclear inclusions on light microscopy. Electron microscopy revealed the inclusions to be rod (nemaline) bodies and were located in 80% of the muscle nuclei. Cytoplasmic rod bodies were also present in 50% of the muscle fibers, often arising from Z discs. The intranuclear rods were more than ten times larger than the cytoplasmic rods. There have been eight reported cases of abundant intranuclear rods in nemaline myopathy: three adult onset; one childhood onset; and four neonatal (including this case). Six of the cases (all of the neonatal and two adult onset) died due to respiratory failure and pneumonia. While intranuclear rods are unusual in nemaline myopathy, they occur in both adult and neonatal cases, and their presence is often associated with a fatal outcome.     

Sporadic late onset nemaline myopathy and immunoglobulin deposition disease

Introduction: In monoclonal gammopathy, organ dysfunction can occur due to deposition of immunoglobulin fragments. A rare form of acquired myopathy often associated with monoclonal gammopathy is sporadic late onset nemaline myopathy (SLONM), which is characterized by nemaline rods in myofibers. The pathogenetic link between monoclonal gammopathy and SLONM has not yet been elucidated. Methods: Case report of a patient with monoclonal gammopathy who developed a progressive myopathy, finally diagnosed as SLONM. Results: A muscle biopsy showed mild myopathic changes. A second biopsy 1 year after clinical onset demonstrated deposition of immunoglobulin light and heavy chains and the presence of nemaline rods. The patient experienced marked improvement of muscle strength after autologous stem cell transplantation and treatment with bortezomib, a therapy that is known to be effective in light chain deposition disease. Conclusions: We speculate that deposition of light and heavy chains, rather than nemaline bodies, has myotoxic effects on skeletal muscle. Muscle Nerve 48 : 983–988, 2013     

Idiopathic adult‐onset nemaline myopathy presenting with isolated respiratory failure

Idiopathic adult‐onset nemaline myopathy is a rare condition of unknown etiology that usually presents with proximal weakness. This case study reports a 60‐year‐old woman who presented with isolated type 2 respiratory failure secondary to bilateral hemidiaphragm weakness. A left vastus medialis muscle biopsy examined under light microscopy revealed appearances typical of nemaline myopathy. Electron microscopy confirmed the presence of nemaline rods in most muscle fibers, thus establishing idiopathic adult‐onset nemaline myopathy as the cause of her respiratory failure. Our patient's presentation highlights the importance of considering neuromuscular weakness as a cause of respiratory failure. Unless appropriate tests are performed—including a muscle biopsy, if indicated—specific neuromuscular diseases are easily missed. This can lead to inappropriate counseling and treatment. Muscle Nerve 39: 406–408, 2009     

Late-onset rod myopathy associated with monoclonal gammopathy

A 31-yr-old woman presented with a severe and rapidly progressive myopathy affecting proximal limbs, neck flexors and respiratory muscles. Muscle biopsy revealed numerous atrophic fibres with marked structural alterations, without inflammatory infiltrate. By electron microscopy, atrophic fibres displayed many rods. A benign monoclonal gammopathy (IgG, lambda chain) was evident in serum. A sarcolemmal deposit of IgG, lambda chain was found by immunostaining. Plasmapheresis and immunosuppressive therapies produced a decrease in paraproteinemia and a partial clinical improvement. This observation is the third to associate monoclonal gammopathy with “late-onset rod myopathy”. The pathogenetic role of paraproteinemia remains unclear.     

A gene for autosomal recessive nemaline myopathy assigned to chromosome 2q by linkage analysis

Clinical genetic evidence suggests the existence of an autosomal recessive form of congenital nemaline myopathy in addition to the autosomal dominant one(s). One mutation in an Australian kindred has been identified as causing an autosomal dominant form of the disease. This mutation in the alpha-tropomyosin gene TPM3 has previously been excluded as causing autosomal recessive nemaline myopathy.

We searched systematically for genetic linkage to autosomal recessive nemaline myopathy (NEM2) by studying microsatellite marker alleles in seven multiplex families from Finland, Denmark, Wales, England and The Netherlands. Significant evidence of linkage was found to markers on chromosome 2q, the highest multipoint lod score value being 5.34 for the marker D2S151. Recombinant genotypes in affected individuals demarcate the region in which the NEM2 gene is likely to reside as a 13 cM region between the markers 132S150 and D2Sl42.

These results confirm the existence of at least one distinctive form of autosomal recessive nemaline myopathy and provide a basis for the identification of its gene.     

Lack of the C-terminal domain of nebulin in a patient with nemaline myopathy

The most common autosomal recessive form of nemaline myopathy is due to mutations in the nebulin gene. Among eight patients studied, we identified one, a 14-year-old girl, with a specific pattern of diffuse rods in muscle fibers. Western blot analysis detected absence of the C-terminal domain of nebulin. Protein analysis may represent a good screening method to direct molecular studies in the case of very large and complex genes such as the large 1298 kb nebulin gene.     

成人型杆状体肌病二例临床病理和超微结构研究

目的 探讨成人型杆状体肌病的临床病理和超微结构特点。方法 对2例成人型杆状体肌病患者的肌肉组织病理和超微结构进行观察。结果 2例患者均以颈肌无力起病，以后四肢和躯干肌不同程度受累，无骨骼发育畸形。肌肉组织病理改变的特点为选择性I型纤维萎缩，改良Gomori三色法染色可见萎缩纤维内含大量深紫色颗粒状物。例1发现大量中央核纤维。电镜观察可见肌原纤维排列紊乱，大量杆状体形成。在例1的肌核内发现核内包涵体，结构特点与胞质内的杆状体相似。结论 成人型杆状体肌病临床缺乏特征性。肌肉病理中央核可与杆状体同时出现，与婴儿型和儿童型杆状体肌病相比，成人型患者肌纤维萎缩明显。肌核内可出现包涵体，其结构与胞质内杆状体一致。     

Magnetic resonance imaging of muscle in nemaline myopathy

We report muscle MRI findings of 10 patients from 8 families with nemaline myopathy. Patients with involvement of the nebulin (NEB) gene showed a consistent pattern of selective muscle involvement corresponding to clinical severity. In mild cases, there was complete sparing of thigh muscles and selective involvement of tibialis anterior and soleus. In moderate cases, there was predominant involvement of rectus femoris, vastus lateralis and hamstring muscles and diffuse involvement of anterior compartment and soleus. Patients with nemaline myopathy secondary to mutations in the skeletal muscle -actin (ACTA1) gene showed diffuse involvement of thigh and leg muscles with relative sparing of the gastrocnemii. Selective muscle involvement in both genetic categories was distinct from what has been reported in other congenital myopathies. We conclude that muscle MRI may be applied to distinguish nemaline myopathy from other conditions with similar clinical and histopathological features, to supplement clinical assessment in individual patients and to help direct genetic testing.     

Homozygosity for a nonsense mutation in the alpha-tropomyosin slow gene TPM3 in a patient with severe infantile nemaline myopathy

The nemaline myopathies are muscle disorders of variable severity and age of onset, with characteristic nemaline bodies in the sarcoplasm. Genes for dominant (NEM1) and recessive (NEM2A) nemaline myopathy have been localised to chromosomes one and two, respectively. A missense mutation in the alpha-tropomyosin gene (TPM3) has been associated with NEM1 in one family. Probands from 76 other nemaline myopathy families have now been screened for TPM3 mutations. One proband, who was not noted to have any weakness neonatally, but who died at 21 months of age, was shown to be homozygous for a single strand conformation polymorphism (SSCP) in skeletal-muscle-specific exon 1 of TPM3. Sequencing revealed homozygosity for a nonsense mutation at codon 31 (CAG to TAG). The patient should have no functioning alpha-tropomyosin slow protein. The nemaline bodies in this patient were exclusively in type one fibres, consistent with the expression of TPM3 only in type one fibres.     

Amyloid myopathy presenting with distal atrophic weakness

Amyloid myopathy is a rare complication of primary amyloidosis usually presenting with proximal muscle weakness. We report a woman with multiple myeloma in whom marked atrophy and weakness of finger flexor muscles were the first manifestations of systemic amyloidosis. Muscle biopsy revealed amyloid angiopathy with deposits of lambda light chains in vessel walls. The recognition of amyloid myopathy is important because clinical symptoms may respond to chemotherapy.     

Homozygosity for a nonsense mutation in the alpha-tropomyosin slow gene TPM3 in a patient with severe infantile nemaline myopathy

The nemaline myopathies are muscle disorders of variable severity and age of onset, with characteristic nemaline bodies in the sarcoplasm. Genes for dominant (NEM1) and recessive (NEM2A) nemaline myopathy have been localised to chromosomes one and two, respectively. A missense mutation in the alpha-tropomyosin gene (TPM3) has been associated with NEM1 in one family. Probands from 76 other nemaline myopathy families have now been screened for TPM3 mutations. One proband, who was not noted to have any weakness neonatally, but who died at 21 months of age, was shown to be homozygous for a single strand conformation polymorphism (SSCP) in skeletal-muscle-specific exon 1 of TPM3. Sequencing revealed homozygosity for a nonsense mutation at codon 31 (CAG to TAG). The patient should have no functioning alpha-tropomyosin slow protein. The nemaline bodies in this patient were exclusively in type one fibres, consistent with the expression of TPM3 only in type one fibres.     

NEB‐related core‐rod myopathy with distinct clinical and pathological features

Introduction: Mutations in the gene encoding nebulin (NEB) are known to cause several types of congenital myopathy including recessive nemaline myopathy and distal nebulin myopathy. Core‐rod myopathy has recently been reported to be another type of NEB‐related myopathy, and is pathologically characterized by the coexistence of cores and nemaline rods within muscle fibers. Methods: We describe 2 patients with core‐rod myopathy who were analyzed genetically by whole exome sequencing and evaluated clinically and pathologically. Findings were compared with those of patients with the disease of other genetic causes. Results: Three NEB mutations were identified, 2 of which were novel. Mild clinical features, unusual patterns of muscle involvement, and atypical pathological findings were observed. Conclusions: We propose that the clinical and pathological spectrum of core‐rod myopathy should be widened. A significant amount of residual nebulin expression is believed to contribute to the much milder phenotype exhibited by the patients we describe here. Muscle Nerve 53: 479–484, 2016     

Clinical and genetic heterogeneity in autosomal recessive nemaline myopathy

Autosomal recessive nemaline (rod) myopathy is clinically and genetically heterogeneous. A clinically distinct, typical form, with onset in infancy and a non-progressive or slowly progressive course, has been assigned to a region on chromosome 2q22 harbouring the nebulin gene. Mutations have now been found in this gene, confirming its causative role. The gene for slow tropomyosin TPM3 on chromosome 1q21, previously found to cause a dominantly inherited form, has recently been found to be homozygously mutated in one severe consanguineous case. Here we wished to determine the degree of genetic homogeneity or heterogeneity of autosomal recessive nemaline myopathy by linkage analysis of 45 families from 10 countries. Forty-one of the families showed linkage results compatible with linkage to markers in the nebulin region, the highest combined lod scores at zero recombination being 14.13 for the marker D2S2236. We found no indication of genetic heterogeneity for the typical form of nemaline myopathy. In four families with more severe forms of nemaline myopathy, however, linkage to both the nebulin and the TPM3 locus was excluded. Our results indicate that at least three genetic loci exist for autosomal recessive nemaline myopathy. Studies of additional families are needed to localise the as yet unknown causative genes, and to fully elucidate genotype-phenotype correlations.